I flipped my PB+ Dual Fans around to the top to cool the extruders. I find if I need it to keep them from not getting too hot and bending and pigtailing filament. That was fine for simple parts in ABS, but I'm looking at PETG and PLA and more parts with bridging and overhangs where I could use the fan.

The extruders need air pretty much constantly. I pulled two fans out of an old PC housing

Looks like it. I've used them to put too many fans in computer cases (somewhere here is a picture of a 200mm case fan, sitting on the same size heated bed, that's probably plugged into one of those). They're popcorn parts, sold all over. Good choice